1. Field of the Invention
The present invention relates to inserts in sandwich structures, particularly inserts which enhance thermal conductivity thereof
2. Description of Related Art
Sandwich construction with composite (graphite resin) face sheets and aluminum or titanium honeycomb have been used to provide high stiffness and low weight structures. Attaching hardware (electrical boxes or other structures) to the sandwich often requires high thermal conductivity between the composite face sheets and attaching hardware. This is especially true in situations where there is no convection, such as spacecraft applications. Inserts are often installed in the sandwich to allow mechanical fasteners (bolts or screws) to be used to hold the hardware to the sandwich. However, typical inserts do not provide the thermal conductivity needed between the composite face sheets and the attaching hardware.
Vendors currently supply a variety of insert sizes and designs (eg., per FIG. 1) but none have been found to meet the thermal conductivity needs of composite sandwich structures. Tests have shown thermal conductance values of about 0.1 W/.degree.C. to be typical with desired values more in the range of 0.5 W/.degree.C.
That is, in spacecraft, motors or other heat generating units are mounted to the walls thereof and need to discharge their heat through such walls and into space to avoid overheating. These units are mounted to the walls by fasteners secured by inserts, eg., as indicated in FIG. 1. Typically, however, the heat generating unit's attaching hardware is not held in sufficient contact with the face sheet(s) of the structure to allow heat to be readily conducted therefrom through the sandwich wall structure as more fully described below with respect to FIG. 1.
Related patents noted herein relative to inserts in spacecraft are U.S. Pat. No. 5,263,538 to M. Amidieu et al (1993), U.S. Pat. No. 5,474,262 to J. Fiore (1995) and U.S. Pat. No. 5,624,088 to J. Fiore (1997). While these references disclose sandwich walls for spacecraft and inserts therefor, no disclosure of employing inserts to enhance thermal conductivity from attaching hardware through a sandwich structure is seen.
Accordingly, there is need and market for thermal conductivity (TC) inserts for sandwich structures that overcomes the above prior art shortcomings.
There has now been discovered a TC insert that serves to increase the contact area between a sandwich face sheet and attaching hardware (AH) so as to provide elevated thermal conductive values therebetween.